Large frame power generation gas turbines that generate power from combustible fuels are often computer controlled through a series of complex algorithms and inputs from various types of sensors, including temperature sensors. Such sensor inputs play an important role in the efficiency and emissions performance of gas turbines.
Conventional large frame ground-based gas turbines use numerous exhaust gas thermocouples for control purposes. The number of sensors can range from sixteen on smaller output engines to as many as thirty on larger engines. Such thermocouples are typically installed in a radiation shield welded to the exhaust plenum of the turbine. The radiation shield design is intended to allow for easy replacement of the protected temperature sensor during maintenance or as a result of premature failure.
To avoid the problem of the temperature sensor seizing inside the radiation shield as a result of high temperature operating conditions, typically the sheath of the sensor and the radiation shield are made from different alloys.